This invention relates to a modular tibial component for use in total knee arthroplasty. More particularly, it relates to a modular tibial component for use in Minimally Invasive Surgery (MIS) wherein all the modular tibial components can be installed through an incision on either the medial side or lateral side or on an anterior-lateral or anterior-medial location on the knee.
As used herein, when referring to bones or other parts of the body, the term “proximal” means closer to the heart and the term “distal” means more distant from the heart. The term “inferior” means toward the feet and the term “superior” means towards the head. The term “anterior” means towards the front part of the body or the face and the term “posterior” means towards the back of the body. The term “medial” means toward the midline of the body and the term “lateral” means away from the midline of the body.
In the past, resurfacing of a knee joint was performed with the implantation of prosthetic femoral and tibial components through an incision extending proximally to distally along the anterior surface of the knee adjacent the lateral or medial sides of the patella. This required a comparatively long incision to be made in order to install the prosthetic femoral and tibial component. Recently, there has been progress towards shortening the incision and moving the incision either medially or laterally from the prior art anterior incision. While direct medial or lateral approaches are possible, it is preferred to have an anterior-medial or anterior-lateral approach.
U.S. Patent Publication No. 2003/0171757 relates to such a minimally invasive total knee arthroplasty method and instrumentation used therefor. In addition, in co-pending U.S. application Ser. No. 10/768,520 assigned to the assignee of the present invention discloses instrumentation for use with such a minimally invasive method.
Incisions size, while of secondary importance to not everting or subluxing the patella, has been reduced and may be in the range of 7-9 cm. Consequently it has been found necessary to utilize femoral and tibial prosthetic implants which are adapted to be inserted through this reduced incision. One way of producing such an implant is to make the typical parts of the implant modular so that they may be inserted into a prepared knee in series. For example, with respect to the tibia, a typical tibial implant includes a stem or a keel, a baseplate and a modular bearing insert typically made of a polymeric material such as ultra-high molecular weight polyethylene.
In the present invention, the stem or keel has been made a separate element from the tibial baseplate which supports the polymeric bearing component with the stem or keel including a coupling feature which can be inserted through an aperture in the baseplate or in the locking element which can preferably be inserted in the medial to lateral or lateral to medial direction is used to lock the coupling feature of the keel to the baseplate and the polymeric bearing insert includes a recess, which can be in the form of an opening, to receive the locking element and the keel coupling element so that these elements are either captured within the polymeric bearing insert or at least do not extend proximally into contact with the femoral component. The same could be accomplished by using a two piece polymeric bearing component having a separate lateral condylar component and medial condylar component with a space in between for receiving the locking element. Of course if an anterior incision is used the locking or coupling element can be inserted in the anterior to posterior direction.
Modular prosthetic knee components are known and are shown in U.S. Pat. No. 5,152,796, U.S. Pat. No. 5,326,359, U.S. Pat. No. 6,258,127, U.S. Pat. No. 6,506,216, and U.S. Pat. No. 5,413,605. These patents relate to methods of attaching modular stems or keels to a femoral or tibial component.
The use of dovetails is also known in prosthetic knee implant applications and such are shown in U.S. Pat. Nos. 4,923,472 and 6,299,645.